reading these boards on how to find siibi I noticed that a LOT of people were asking how to marry Lydia and if it was possible.
IT IS NOT possible even though it is apparently listed in a ton of lists.
HOWEVER if you are on the PC, you can set her available for marriage and you can do the same for I'm guessing almost any character. PLEASE BE CAREFUL when doing this. I am in no way responsible for the effects and It wouldn't surprise me if the game crashes when it tries to house your "dragon-wife-husband" in your whiterun house. Also beware that it might initially work but down the line if the character is special in any way it might cause problems. I also have no idea how interactions such as the shop or whatnot will behave. ---SAVE---
So here's how you do it.
First open the console ( ` ) key, which is located to the left of the number 1 that is above the letter Q in English keyboards. If this doesn't open it, google "Skyrim Open Console X Language" where X is your language.
Now Left click on the character you wish to make available for marriage. ---MAKE SURE you are selecting the character.--- Sometimes weapons or even a butterfly gets in the way!!!
Now type
Addfac 19809 1
Hit Enter
Aaaand you're done. Tried it on some random NPC, worked fine, they even established some random shop (Solid Coding, Bethesda), but they couldn't accompany you out (although I don't know if it's standard).
*PLEASE NOTE - You still need the amulet of Mara (found in riften, a priest sells it to you) and to be wearing said amulet. You also need to wait around 24 hours after you request the marriage for it to start! -
Salutations